1. Field of the Invention
The present invention relates to a water base ink for ink-jet recording to be used for an ink-jet recording apparatus and an ink-jet recording apparatus which accommodates the same.
2. Related Art
In the ink-jet recording system, ink droplets are formed by using an ink discharge method including, for example, the electrostatic attraction method, the method in which mechanical vibration or displacement is applied to the ink by using a piezoelectric element, and the method in which bubbles are generated by heating the ink to utilize the pressure generated thereby, and all or a part of the ink droplets are adhered to an objective recording material such as paper to perform the recording.
Those known as the ink for ink-jet recording to be used for the ink-jet recording system as described above include those obtained by dissolving or dispersing a water-soluble dye or a pigment in a liquid medium composed of water and a water-soluble organic solvent. The ink for ink-jet recording as described above is required to have the optimum performance characteristics to be used for the ink-jet recording method. Specifically, for example, the following features are required. That is, when an image is formed on the recording paper, a high printing quality is obtained with a sharp outline or contour of the image without causing any irregular flow of the ink along the fibers of the recording paper or any irregular permeation of the ink into the spaces between the fibers (hereinafter referred to as “feathering” as well). When an image is formed on the recording paper, then the ink is quickly dried, and the rub resistance (property which allows the image to be not disturbed when the paper having the image formed with the ink is rubbed) is satisfactory. No corrosion is caused on metal material and resin material which are used for the ink-jet head, and it is possible to perform stable jetting operation for a long period of time without causing any clog-up at the nozzle.
Many techniques have been hitherto used in order to satisfy the performance characteristics as described above. Japanese Patent Application Laid-open No. 8-259864 discloses a technique in which the permeability of an ink is suppressed on the recording paper surface by increasing the surface tension of the ink to obtain a high printing quality in which the feathering is scarcely caused. However, the following problem has arisen due to the slow permeation of the ink into the recording paper. That is, the drying performance is deteriorated and the rub resistance is deteriorated. On the other hand, Japanese Patent Application Laid-open No. 2001-226617 discloses a technique in which the permeability of an ink is improved to obtain the quick drying performance while maintaining a high printing quality in which the feathering is scarcely caused by using a surfactant having unsaturated bond and a surfactant having secondary or tertiary alkyl group in combination.
The discharge head of the ink-jet printer, which is based on the use of the piezoelectric element, has such a structure that the metal member makes direct contact with the ink in many cases. In particular, when the water base ink is used, the following problem has arisen. That is, the metal member is corroded by the water base ink to consequently cause the discharge failure and the clog-up at the filter and the nozzle in some cases.
However, it has been difficult for the conventional ink to satisfy all characteristics of the high printing quality with less feathering, the rub resistance of the recorded image, and the long term nozzle discharge stability brought about by the suppression of metal corrosion. The following situation has been sometimes caused. That is, the feathering occurs on the recorded image, the outline is not sharp, and the printing quality is deteriorated depending on the type of the added surfactant.